Is Lysine Similar to Tryptophan?

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Lysine and tryptophan share a few similarities. They're both amino acids used to build proteins -- and they're essential, which means you must get them from your diet because your body can’t produce them. You have a greater chance of not getting enough lysine and tryptophan than other amino acids, which makes both of them limiting amino acids. Otherwise, they each have unique functions.

Lysine

In addition to building proteins, lysine is essential for the production of a substance called carnitine. Almost every cell in your body depends on carnitine. It transports fats into the cells so that the fats can metabolize for energy. Lysine also helps your body absorb calcium and make collagen, which is a connective tissue used to build bones and support the skin and tissues. In large doses of 3 grams daily, lysine supplements may help treat herpes by reducing the number and intensity of flare-ups, according to the New York University Langone Medical Center website.

Tryptophan

When you consume tryptophan, your body converts it into serotonin. Since it’s a mood-regulating neurotransmitter, low levels of serotonin can lead to depression. A deficiency in tryptophan, and the subsequent lack of serotonin, is also associated with general irritability, according to a study published in the July 2006 issue of the “Journal of Psychiatry and Neuroscience.” Tryptophan affects your sleep cycle because you use serotonin to synthesize the hormone melatonin. When you produce high levels of melatonin at night, it can help you relax and sleep. Your body can also convert tryptophan into the B vitamin niacin.

Requirements

Adults should consume 30 milligrams of lysine and 4 milligrams of tryptophan per kilogram of body weight, according to the World Health Organization. It’s hard to track your intake because individual amino acids are not listed on nutrition facts labels. The best way to ensure that you get the amount you need is by consuming the recommended dietary allowance for protein. For women that means consuming 46 grams of protein each day, while men need 56 grams.

Sources

Compared to the amount of other amino acids, foods contain a smaller quantity of tryptophan. Lysine content is low in the most common grains: corn, rice, wheat and oats. Your body uses amino acids in a specific ratio to each other, so low levels of lysine or tryptophan affect your body’s ability to use other amino acids. This is why they're called limiting amino acids. The best sources of both lysine and tryptophan are meat, poultry, fish and dairy products. Other good sources of tryptophan include beans, broccoli, peas, nuts, spinach and other leafy greens. Beans and legumes are good choices for lysine.

About the Author

Sandi Busch received a Bachelor of Arts in psychology, then pursued training in nursing and nutrition. She taught families to plan and prepare special diets, worked as a therapeutic support specialist, and now writes about her favorite topics – nutrition, food, families and parenting – for hospitals and trade magazines.